Unlike conventional homogeneous nanograined (NG) materials, gradient structured materials combine high strength and ductility. The gradient nanograined (GNG) structures are divided into three zones by grain size: the small‐grained zone, the transition‐grained zone, and the large‐grained zone. Molecular dynamics (MD) simulation is performed to investigate the effect of the widths of zones on the strength of GNG structures with different grain sizes. The simulation results reveal the strengthening mechanism of GNG structures from the perspective of microstructure evolution. With the change in grain size, the dominant deformation mode changes from grain boundary (GB) activities in the mall‐grained zone to dislocation slip in the large one. The inverse Hall–Petch phenomenon is observed during plastic deformation. Synergistic strengthening of dislocation and heterodeformation induced (HDI) can be achieved in the structure by regulating the widths of zones with different grain sizes.

The distribution of grains plays a crucial role in determining the strength of polycrystalline copper when the grain size is constant. Herein, the mechanical properties of homogeneous nano‐grained (HNG) and gradient nano‐grained (GNG) coppers with different grain distributions are examined using molecular dynamics (MD) simulations. The HNG‐ordered structure has all triple junctions (TJs), whereas the random structure contains many quadruple and quintuple junctions. When grain size is below the critical size in the inverse Hall–Petch relationship, the high‐density TJs in the HNG‐ordered structure effectively inhibit grain boundary (GB) softening compared with the random structure, leading to higher strength. However, when grain size is above the critical size, subgrains are produced inside the large grains due to dislocation slip. In addition, disordered atoms in HNG‐random structure are stacked in the quadruple and quintuple junctions, resulting in thicker GBs. This triggers grain boundary migration, and forms more subgrains at GBs. Subsequently, grain boundary sliding and grain rotation of subgrains induce partial recrystallization in the structure. This consecutively triggered deformation mechanism leads to extra strengthening in the random structure. Further research indicates that combining small‐grained ordered and large‐grained random structures can be a new approach to effectively strengthen GNG materials.